Iron-oxidized hard disk drive enclosure cover

ABSTRACT

An iron-oxidized hard disk drive (HDD) cover has an inner surface that is substantially free of un-oxidized or pure metallic iron, fabricated by baking a stainless steel cover and thereby oxidizing the cover surface of iron. Because the cover is iron-oxidized, a costly nickel-plating process may be foregone while a “Fe smear” problem may be significantly reduced. Such an iron-oxidized cover is especially beneficial for, though not limited to, use as an inner cover in a sealed HDD.

FIELD OF EMBODIMENTS

Embodiments of the invention may relate generally to hard disk drivesand more particularly to an iron-oxidized cover for prevention orreduction of iron contamination.

BACKGROUND

A hard-disk drive (HDD) is a non-volatile storage device that is housedin a protective enclosure and stores digitally encoded data on one ormore circular disk having magnetic surfaces. When an HDD is inoperation, each magnetic-recording disk is rapidly rotated by a spindlesystem. Data is read from and written to a magnetic-recording disk usinga read/write head that is positioned over a specific location of a diskby an actuator. A read/write head uses a magnetic field to read datafrom and write data to the surface of a magnetic-recording disk. Writeheads make use of the electricity flowing through a coil, which producesa magnetic field. Electrical pulses are sent to the write head, withdifferent patterns of positive and negative currents. The current in thecoil of the write head induces a magnetic field across the gap betweenthe head and the magnetic disk, which in turn magnetizes a small area onthe recording medium.

Some HDDs employ a stainless steel cover, in conjunction with a base, toform the HDD enclosure. Steel is composed primarily of iron with someamount of carbon. Thus, stainless steel is a steel alloy composed ofsteel, i.e., iron, with a certain amount of chromium. Stainless steeldoes not readily corrode and oxidize (i.e., rust), as compared toordinary steel, and therefore is often a reasonable choice for an HDDcover. However, stainless steel is not corrosion-proof or rust-proof andthus there is a phenomenon in HDD technology referred to as “Fe smear”or “iron smear”. With Fe smear, iron contamination migrates from thecover, for example, to the slider and/or disk which in turn can causesweak write operations. Weak write operations are at some degreeconsidered an HDD failure, which has a direct effect on the reliabilityof the drive. Therefore, there are challenges associated with inhibitingFe smear in HDDs.

Any approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection.

SUMMARY OF EMBODIMENTS

Embodiments of the invention are directed toward an iron-oxidized harddisk drive (HDD) cover, a hard disk drive comprising such a cover, andassociated methods for manufacturing such a cover. An iron-oxidized HDDcover according to embodiments comprises an inner surface that issubstantially free of un-oxidized, or “pure”, metallic iron. Accordingto embodiments, the iron-oxidized cover is manufactured by baking astainless steel cover, thereby oxidizing the cover surface of iron. Forexample and according to an embodiment, the iron oxide concentration onthe surface of the cover may be at least about ten times the chromiumoxide concentration. Consequently, because the cover is iron-oxidized arelatively expensive nickel-plating process may be foregone while the Fesmear problem may be significantly reduced. Furthermore, such aniron-oxidized cover is especially beneficial for, though not limited to,use as an inner cover in a sealed HDD.

Embodiments discussed in the Summary of Embodiments section are notmeant to suggest, describe, or teach all the embodiments discussedherein. Thus, embodiments of the invention may contain additional ordifferent features than those discussed in this section. Furthermore, nolimitation, element, property, feature, advantage, attribute, or thelike expressed in this section, which is not expressly recited in aclaim, limits the scope of any claim in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a plan view illustrating a hard disk drive, according to anembodiment;

FIG. 2 is a diagram illustrating a method for manufacturing a hard diskdrive cover, according to an embodiment; and

FIG. 3 is an exploded view illustrating a sealed hard disk drive,according to an embodiment.

DETAILED DESCRIPTION

Approaches to an iron-oxidized hard disk drive cover to inhibit ironcontamination are described. In the following description, for thepurposes of explanation, numerous specific details are set forth inorder to provide a thorough understanding of the embodiments of theinvention described herein. It will be apparent, however, that theembodiments of the invention described herein may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring the embodiments of the invention described herein.

Physical Description of Illustrative Operating Environments

Embodiments may be used for, but are not limited to, an enclosure coverfor a hard-disk drive (HDD) storage device. Thus, in accordance with anembodiment, a plan view illustrating an HDD 100 is shown in FIG. 1 toillustrate an exemplary operating environment.

FIG. 1 illustrates the functional arrangement of components of the HDD100 including a slider 110 b that includes a magnetic-reading/recordinghead 110 a. Collectively, slider 110 b and head 110 a may be referred toas a head slider. The HDD 100 includes at least one head gimbal assembly(HGA) 110 including the head slider, a lead suspension 110 c attached tothe head slider typically via a flexure, and a load beam 110 d attachedto the lead suspension 110 c. The HDD 100 also includes at least onemagnetic-recording medium 120 rotatably mounted on a 124 and a drivemotor (not visible) attached to the spindle 124 for rotating the medium120. The head 110 a includes a write element and a read element forrespectively writing and reading information stored on the medium 120 ofthe HDD 100. The medium 120 or a plurality of disk media may be affixedto the spindle 124 with a disk clamp 128.

The HDD 100 further includes an arm 132 attached to the HGA 110, acarriage 134, a voice-coil motor (VCM) that includes an armature 136including a voice coil 140 attached to the carriage 134 and a stator 144including a voice-coil magnet (not visible). The armature 136 of the VCMis attached to the carriage 134 and is configured to move the arm 132and the HGA 110, to access portions of the medium 120, being mounted ona pivot-shaft 148 with an interposed pivot-bearing assembly 152. In thecase of an HDD having multiple disks, the carriage 134 is called an“E-block,” or comb, because the carriage is arranged to carry a gangedarray of arms that gives it the appearance of a comb.

An assembly comprising a head gimbal assembly (e.g., HGA 110) includinga flexure to which the head slider is coupled, an actuator arm (e.g.,arm 132) and/or load beam to which the flexure is coupled, and anactuator (e.g., the VCM) to which the actuator arm is coupled, may becollectively referred to as a head stack assembly (HSA). An HSA may,however, include more or fewer components than those described. Forexample, an HSA may refer to an assembly that further includeselectrical interconnection components. Generally, an HSA is the assemblyconfigured to move the head slider to access portions of the medium 120for read and write operations.

With further reference to FIG. 1, electrical signals (e.g., current tothe voice coil 140 of the VCM) comprising a write signal to and a readsignal from the head 110 a, are provided by a flexible interconnectcable 156 (“flex cable”). Interconnection between the flex cable 156 andthe head 110 a may be provided by an arm-electronics (AE) module 160,which may have an on-board pre-amplifier for the read signal, as well asother read-channel and write-channel electronic components. The AE 160may be attached to the carriage 134 as shown. The flex cable 156 iscoupled to an electrical-connector block 164, which provides electricalcommunication through electrical feedthroughs provided by an HDD housing168. The HDD housing 168, also referred to as a base, in conjunctionwith an HDD cover provides a sealed, protective enclosure for theinformation storage components of the HDD 100.

Other electronic components, including a disk controller and servoelectronics including a digital-signal processor (DSP), provideelectrical signals to the drive motor, the voice coil 140 of the VCM andthe head 110 a of the HGA 110. The electrical signal provided to thedrive motor enables the drive motor to spin providing a torque to thespindle 124 which is in turn transmitted to the medium 120 that isaffixed to the spindle 124. As a result, the medium 120 spins in adirection 172. The spinning medium 120 creates a cushion of air thatacts as an air-bearing on which the air-bearing surface (ABS) of theslider 110 b rides so that the slider 110 b flies above the surface ofthe medium 120 without making contact with a thin magnetic-recordinglayer in which information is recorded.

The electrical signal provided to the voice coil 140 of the VCM enablesthe head 110 a of the HGA 110 to access a track 176 on which informationis recorded. Thus, the armature 136 of the VCM swings through an arc180, which enables the head 110 a of the HGA 110 to access varioustracks on the medium 120. Information is stored on the medium 120 in aplurality of radially nested tracks arranged in sectors on the medium120, such as sector 184. Correspondingly, each track is composed of aplurality of sectored track portions (or “track sector”), for example,sectored track portion 188. Each sectored track portion 188 may becomposed of recorded data and a header containing a servo-burst-signalpattern, for example, an ABCD-servo-burst-signal pattern, which isinformation that identifies the track 176, and error correction codeinformation. In accessing the track 176, the read element of the head110 a of the HGA 110 reads the servo-burst-signal pattern which providesa position-error-signal (PES) to the servo electronics, which controlsthe electrical signal provided to the voice coil 140 of the VCM,enabling the head 110 a to follow the track 176. Upon finding the track176 and identifying a particular sectored track portion 188, the head110 a either reads data from the track 176 or writes data to the track176 depending on instructions received by the disk controller from anexternal agent, for example, a microprocessor of a computer system.

An HDD's electronic architecture comprises numerous electroniccomponents for performing their respective functions for operation of anHDD, such as a hard disk controller (“HDC”), an interface controller, anarm electronics module, a data channel, a motor driver, a servoprocessor, buffer memory, etc. Two or more of such components may becombined on a single integrated circuit board referred to as a “systemon a chip” (“SOC”). Several, if not all, of such electronic componentsare typically arranged on a printed circuit board that is coupled to thebottom side of an HDD, such as to HDD housing 168.

References herein to a hard disk drive, such as HDD 100 illustrated anddescribed in reference to FIG. 1, may encompass a data storage devicethat is at times referred to as a “hybrid drive”. A hybrid drive refersgenerally to a storage device having functionality of both a traditionalHDD (see, e.g., HDD 100) combined with solid-state storage device (SSD)using non-volatile memory, such as flash or other solid-state (e.g.,integrated circuits) memory, which is electrically erasable andprogrammable. As operation, management and control of the differenttypes of storage media typically differs, the solid-state portion of ahybrid drive may include its own corresponding controller functionality,which may be integrated into a single controller along with the HDDfunctionality. A hybrid drive may be architected and configured tooperate and to utilize the solid-state portion in a number of ways, suchas, for non-limiting examples, by using the solid-state memory as cachememory, for storing frequently-accessed data, for storing I/O intensivedata, and the like. Further, a hybrid drive may be architected andconfigured essentially as two storage devices in a single enclosure,i.e., a traditional HDD and an SSD, with either one or multipleinterfaces for host connection.

Introduction

As mentioned, some hard disk drives (HDDs) employ a stainless steelcover, in conjunction with a base, to form the HDD enclosure. However,use of stainless steel can cause iron (Fe) contamination (“Fe smear”)within the HDD. Such iron contamination is especially problematic insealed HDDs, in which the integrity of the surface of the stainlesssteel cover is degraded when stored in such an oxygen-depletedenvironment. One possible approach to preventing the iron contaminationproblem could be to nickel (Ni) plate the cover. However, nickel-platingis a relatively costly process within HDD manufacturing and, therefore,not ideal.

Method of Manufacturing a Hard Disk Drive Cover

FIG. 2 is a diagram illustrating a method for manufacturing a hard diskdrive cover, according to an embodiment. FIG. 2 characterizes a singlestep process, thus a single block is illustrated.

At block 202, a stainless steel HDD cover part is baked in order tofully oxidize the iron on the surface of the cover part. Being stainlesssteel, the surface of an unbaked cover part in original form contains“pure” metallic iron (Fe), i.e., un-oxidized iron. By contrast, thesurface of the baked cover part no longer contains pure metallic ironbut now contains only, or primarily, oxidized iron. To “fully oxidize”is intended to encompass the possibility that some remnants of metalliciron (Fe) may still exist on the cover, therefore, a “substantiallyfully oxidized” cover part by way of baking is contemplated. Any and alloxidation of the pure metallic iron leads to a scenario in which theproblem of Fe smear is significantly diminished if not outrighteliminated. Furthermore, the expensive luting process can be avoided ifthe process of FIG. 2 is implemented, where such a baking process wouldtypically be considerably less costly than the nickel-plating process.Thus, according to an embodiment, the stainless steel cover part is notnickel-plated.

As discussed, stainless steel contains some amount of chromium.Furthermore, untreated or unbaked stainless steel parts would typicallycontain iron and chromium oxides (e.g., due to atmospheric oxidation) inaddition to the pure metal forms of iron and chromium on their surface.Both of the metallic iron and metallic chromium are oxidized by thebaking procedure, but the overall end aunt of iron oxide increases whilethe overall end amount of chromium oxide decreases by baking. Thus,according to an embodiment, the baking procedure referred to at block202 is such that the iron oxide concentration on the surface of thecover part is at least about ten (10) times the chromium oxideconcentration. A goal of achieving an iron oxide concentration tochromium oxide concentration of over ten (10) times is contemplated andfound to be achievable.

For guidance, but as non-limiting examples, the surface of one unbakedsample contained around 69% iron oxide, 21% chromium oxide, and 3% ironmetal (with the remainder being some nickel, manganese, and chromiummetal), with an iron oxide-to-chromium oxide ratio of about 3.3. Afterbaking at 200° C. for around 3 hours, the sample contained around 85%iron oxide, 11% chromium oxide, and 0% iron metal (with the remainderbeing some manganese), with an iron oxide-to-chromium oxide ratio ofabout 7.9. With a similar unbaked sample, after baking at 250° C. foraround 2 hours, the sample contained around 93% iron oxide, 5% chromiumoxide, and 0% iron metal (with the remainder being some manganese), withan iron oxide-to-chromium oxide ratio of about 18. Furthermore, a bakingtemperature of at least around 230° C. may provide appropriate levels ofiron oxidation, such as leaving iron oxide-to-chromium oxide ratiosgreater than around 10.

A number of approaches may be used to detect the presence of, or in thiscase the absence of, metallic iron on the surface of the cover part. Fora non-limiting example, an XPS (X-ray Photoelectron Spectroscopy) methodmay be used.

Iron-Oxidized HDD Cover

Implementation of the method of manufacturing a hard disk drive (HDD)cover as illustrated in FIG. 2 is likely to result in an iron-oxidizedcover for an HDD, according to an embodiment, where at least the innersurface of the cover is substantially free of un-oxidized iron (i.e.,pure metallic Fe).

As discussed, iron contamination such as “Fe smear” is especiallyproblematic in sealed HDDs, in which the integrity of the surface of thestainless steel cover is degraded when stored in such an oxygen-depletedenvironment. In particular, it is likely that the top disk and theuppermost slider and corresponding read/write head are particularlyafflicted with Fe smear due at least in part to their close proximity tothe top cover part.

HDDs are being manufactured which are hermetically sealed with heliuminside. Further, other gases that are lighter than air have beencontemplated for use as a replacement for air in sealed HDDs. Forexample, with helium having roughly one-seventh the density of air,sealing an HDD with helium significantly reduces the turbulence withinthe drive caused by the spinning disk(s), reduces power consumption andresults in a lower temperature within the HDD.

Based on the foregoing, embodiments are especially suited for, but notlimited to, use with a sealed HDD. FIG. 3 is an exploded viewillustrating a sealed hard disk drive, according to an embodiment.

Sealed hard disk drive (HDD) 300, described in a simplified form,comprises a base 302 to which an electronic circuit board 304 isaffixed, and an actuator 306 such as a voice coil motor (VCM) foractuating the movement of a head-stack assembly (HSA) 308, including ahead slider, over certain locations of one or more disk of a disk stack310, which is mounted on a spindle of a spindle motor 312 by way of adisk clamp 314. The foregoing components may be similar in function tolike components described in reference to FIG. 1 and, along with othercomponents, are enclosed in an enclosure comprising a first cover 316attached to the base 302. According to an embodiment, first cover 316 isimplemented as an iron-oxidized cover part as described herein, such asin reference to FIG. 2, which is a baked stainless steel part that issubstantially free of un-oxidized iron.

With further reference to FIG. 3, according to an embodiment sealed HDD300 comprises a second cover 318 positioned over and/or affixed to thefirst cover 316 to form a hermetically sealed enclosure. For anon-limiting example, the second cover 318 may be sealed onto the firstcover 316 of the enclosure, or onto the base, using an adhesive. Thus,sealed HDD 300 may be filled with a gas lighter than air according to anembodiment, and may be filled with helium according to a relatedembodiment. Note that there may be other technologies associated withhermetically sealing an HDD enclosure to maintain the supply of arelatively low density gas such as helium within the HDD, such as use ofvarious filters, fasteners, adhesives, seals, and the like. Therefore,the manner in which a sealed drive is hermetically sealed may vary fromimplementation to implementation.

Extensions and Alternatives

In the foregoing description, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. Therefore, various modifications andchanges may be made thereto without departing from the broader spiritand scope of the embodiments. Thus, the sole and exclusive indicator ofwhat is the invention, and is intended by the applicants to be theinvention, is the set of claims that issue from this application, in thespecific form in which such claims issue, including any subsequentcorrection. Any definitions expressly set forth herein for termscontained in such claims shall govern the meaning of such terms as usedin the claims. Hence, no limitation, element, property, feature,advantage or attribute that is not expressly recited in a claim shouldlimit the scope of such claim in any way. The specification and drawingsare, accordingly, to be regarded in an illustrative rather than arestrictive sense.

In addition, in this description certain process steps may be set forthin a particular order, and alphabetic and alphanumeric labels may beused to identify certain steps. Unless specifically stated in thedescription, embodiments are not necessarily limited to any particularorder of carrying out such steps. In particular, the labels are usedmerely for convenient identification of steps, and are not intended tospecify or require a particular order of carrying out such steps.

What is claimed is:
 1. A hard disk drive comprising: a base; at leastone disk media rotatably mounted on a spindle; a head slider comprisinga read/write head configured to read from and to write to said diskmedia; a voice coil actuator configured to move said head slider toaccess portions of said disk media; and a pre-oxidized cover coupledwith said base to form an enclosure for said disk media, head slider andvoice coil actuator, wherein a surface of said pre-oxidized cover issubstantially free of un-oxidized metallic iron.
 2. The hard disk driveof claim 1, wherein an iron oxide concentration on said surface of saidpre-oxidized cover is at least about ten times a chromium oxideconcentration of said surface of said pre-oxidized cover.
 3. The harddisk drive of claim 1, wherein said pre-oxidized cover is composed ofbaked stainless steel.
 4. The hard disk drive of claim 1, wherein saidpre-oxidized cover is not nickel-plated.
 5. The hard disk drive of claim1, wherein said pre-oxidized cover is a first cover, said hard diskdrive further comprising: a second cover affixed to said first cover toform a hermetically sealed enclosure.
 6. The hard disk drive of claim 5,wherein said sealed enclosure is substantially filled with a gas that islighter than air.
 7. The hard disk drive of claim 5, wherein said sealedenclosure is substantially filled with a predominantly helium gas.
 8. Aniron-oxidized cover for a hard disk drive enclosure, said covercomprising: an inner surface substantially free of un-oxidized iron,wherein an iron oxide concentration on said inner surface is at leastabout ten times a chromium oxide concentration of said inner surface. 9.The iron-oxidized cover of claim 8, wherein said iron-oxidized cover iscomposed of baked stainless steel.
 10. The iron-oxidized cover of claim9, wherein said iron-oxidized cover is not nickel-plated.
 11. A methodof manufacturing a cover for a hard disk drive, the method comprising:baking a stainless steel cover part to substantially fully oxidize ironon a surface of said cover part, such that an iron oxide concentrationon said surface is at least about 10 times a chromium oxideconcentration on said surface.
 12. The method of claim 11, wherein saidstainless steel cover part is not nickel-plated.